1. Field of the Invention
The present invention relates to new substituted xanthines of formula

the tautomers, the enantiomers, the mixtures thereof, the salts thereof and the hydrates thereof, particularly the physiologically acceptable salts thereof with inorganic or organic acids, such as hydrochlorides, for example, which have valuable pharmacological properties, particularly an inhibiting effect on the activity of the enzyme dipeptidylpeptidase-IV (DPP-IV), the preparation thereof, the use thereof for preventing or treating illnesses or conditions connected with an increased DPP-IV activity or capable of being prevented or alleviated by reducing the DPP-IV activity, particularly type I or type II diabetes mellitus, the pharmaceutical compositions containing a compound of general formula (I) or a physiologically acceptable salt thereof and processes for the preparation thereof.
2. Description of the Prior Art
Xanthine derivatives with an inhibitory effect on DPP-IV are already known from WO 02/068420, WO 02/02560, WO 03/004496, WO 03/024965, WO 04/018468, WO 04/048379, JP 2003300977 and EP 1 338 595, which references are incorporated herein by reference in their entireties.